Lifting body aircraft

ABSTRACT

Take-off and landing distances of a lifting body are significantly reduced by providing a downwardly deflectable inboard control surface at the trailing edge to control lift, and upwardly deflectable control surfaces, outboard in relation to the inboard control surface, to control pitching moment, and thereby adjust angle of attack. A control system not only allows a preliminary &#39;&#39;&#39;&#39;trim&#39;&#39;&#39;&#39; adjustment of all three surfaces but permits the outboard surfaces to be adjusted by the pilot to control the aircraft in flight.

United States Patent [191 Putman Sept. 25, 1973 LIFTING BODY AIRCRAFT[75] Inventor: William F. Putman, Princeton, NJ.

[73] Assignee: Aereon Corporation, Princeton, NJ.

[22] Filed: Aug. 2, 9171 [21] App]. No.: 168,193

[52] US. Cl. 244/13, 244/36 R, 244/75 R, 244/83 R [51] Int. Cl. B64c9/12 [58] Field of Search 244/13, 25, 36, 40 R, 244/76 R, 83 R, 83 B, 83C, 75 R [56] References Cited 1 UNITED STATES PATENTS 2,339,521 1/1944Ross 244/83 B 2,406,588 8/1946 Comelius..... 2,438,309 3/1948 Zimmerman244/13 3,276,722 10/1966 Eggers et al. 244/36 12/1969 Fitzpatrick et al244/25 10/1970 Garren et a1 244/76 R Primary Examiner-Mi]ton BuchlerAssistant ExaminerBarry L. Kelmachter Att0rney--Smith, Harding, Earley &Follmer 5 7] ABSTRACT Take-off and landing distances of a lifting bodyare significantly reduced by providing a downwardly deflectable inboardcontrol surface at the trailing edge to control lift, and upwardlydeflectable control surfaces, outboard in relation to the inboardcontrol surface, to control pitching moment, and thereby adjust angle ofattack. A control system not only allows a preliminary trim adjustmentof all three surfaces but permits the outboard surfaces to be adjustedby the pilot to control the aircraft in flight.

8 Claims, 3 Drawing Figures PATENIED$EP25I975 3.761341 INVENTOR WILLIAMF. PUTMAN BY 5m 11% 2m @W ATTORNEYS LIFTING BODY AIRCRAFT BACKGROUND OFTHE INVENTION This invention relates to aircraft and particularly to alifting body, that is an aircraft having a substantially continuousairfoil surface from one-end of its span to the other and lacking awell-defined transition between wing and fuselage. A typical liftingbody is described in U.S. Pat. No. 3,486,719 issued Dec. 30, 1969 toJohn R. Fitzpatrick and Juergen K. Bock. The lifting body described inthat patent is characterized by a substantially triangular ordelta-shaped planform, a nose at one corner of the triangle and atrailing edge opposite the nose and extending between a pair of lateralextremities, each at one of the remaining comers of the triangle. Thesides of the triangle which meet at the nose form portions of theleading edge, and vertical, longitudinal sections of the lifting bodyare [thick airfoil sections which may be either cambered or, uncambered.The lifting body preferably comprises'an enclosed hull substantiallysymmetrical about a central vertical plane extending from its nose to amid-point at the wide end opposite the nose. The transversecross-sections throughout substantially all of the length of the liftingbody are substantially elliptical Ol'lfillhf side of the centralvertical plane. From the nose to the point of maximum vertical dimensionin the central vertical plane, the elliptical cross-sections becomeprogressively higher and progressively wider, with width increasing morerapidly than height. From the point of maximum vertical dimension towardthe trailing edge, however, the elliptical cross-sections continue to increase progressively in width, but decrease progressively in height.

Various deviations from the above-described relationships may exist in alifting body, for example, with respect to the configuration of the noseand lateral 'ex-' tremities.

Such lifting bodies are designed for longitudinal static stability,possess favorable stall characteristics, and are capable of relativelyhigh cruising speeds and relatively low landing speeds. They can be madeto carry a large payload efficiently, and may be operatedheavier-than-air, or, with helium, either lighteFthan-air or slightlyheavier-than-air.

It is well-recognized that a positive (nose-up) pitching moment isrequired to maintain a positive angle of attack in a longitudinallystatically stable aircraft. In a lifting body having a low aspect ratio,the generation of a positive pitching moment by upward deflection of ahorizontal control surface located on the trailing edge would ordinarilygive rise to a large, downwardly directed lift because of the basic liftdistribution, produced by such a deflection, acting on the large airfoilsurface forward of the control surface. Conversely, the downwarddeflection of such a horizontal control surface in order to increaselift would produce a negative pitching moment tending to reduce theangle of attack. These conditions result in relatively high landing andtake-off speeds and distances.

In accordance with this invention, the impairment of lift which wouldresult from the upward deflection of control surfaces is minimized byproviding at least one additional downwardly deflectable horizontalcontrol surface at the trailing edge in a central location, and bylocating the upwardly deflectablecontrol surfaces at an outboardlocation laterally remote from the central axis of the lifting body,.orat some other location which insures a reduced airfoil surface areaforward of the upwardly deflectable control surfaces, thereby reducingthe resultant downward lift, and also increasing the effectiveness ofthe upwardly deflectable surfaces or of the upwardly deflectablesurfaces together with their associated forward surfaces in producing apositive pitching moment and thereby maintaining a positive angle ofattack.

The downward deflection of the centrally-located control surfaceproduces a pressure differential between the upper and lower surfaces ofthe large airfoil surface area ahead of the central control surface thatis nearly uniform in the streamwise: direction. This pressuredistribution produces a resultant lift force acting very nearly at themid point of the chord line connecting the nose and the trailing edge ofthe airfoil surface in the region of the central control surface. Sincefor a stable delta-shaped aircraft, the center of gravity must also lienear this mid-chord point the resultant lift force produced by thedownwash deflection of the central control surface will produce verylittle pitching moment about the center of gravity of the aircraft.Thus, the downwardly deflectable centrally-located control surfaceproduces lift with relatively little tendency to counteract the effectof the upwardly deflected surfaces, i.e., with relatively littletendency to reduce the positive pitching moment and consequent abilityof the aircraft to maintain a positive angle of attack.

A control system is provided which permits a trimming adjustment to bemade whereby, assuming a neutral stick, the centrally located controlsurface is deflected downwardly to a desired extent,-and the outboardcontrol surfaces are deflected upwardly to an extent depending on thedownward deflection of the centrally located surface. While downwarddeflection of 1 the centrally located surface produces an increasedlift,

it will also produce a negative pitching moment unless the center ofgravity is located sufficiently aft to prevent it. The control systemdeflects the outboard control surfaces to the extent necessary tocompensate for the downward pitching moment, and to produce a constantlyincreasing pitching moment as the control lever is moved away from itsneutral position.

While the control system alone determines the position of the centrallylocated control surface, the outboard control surfaces can be movedabout their preliminary settings as determined by "the preliminarytrimming adjustment, by the pilots stick for the usual control ofbanking and elevation.

The outboard control surfaces may be positioned ei ther on the trailingedge of the lifting body, or on auxiliary surfaces, or they may takeother forms; for example, pivotable fin-like tips.

The outboard surfaces may be permanently in an upwardlydeflectedcondition. The surfaces may be adjustable only on the ground, but arepreferably adjustable in flight by means of a control system whichsimul-. taneously controls the inboard and outboard surfaces.

The principal object of the invention is to reduce the take-off andlanding speeds of a lifting body. Further BRIEF DESCRIPTION OF THEDRAWINGS FIG. 1 is a perspective view of a lifting body equipped with aset of control surfaces in accordance with the invention;

FIG. 2 is a perspective view of a lifting body showing an alternativearrangement of control surfaces in accordance with the invention; and

FIG. 3 is a perspective view showing apparatus for controlling thedeflection of the various control surfaces in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a delta-shapedlifting body 4 comprising an enclosed hull 6, having a nose 8 and atrailing edge 10. Vertical stabilizers l2 and 14 are provided at thelateral extremities of the lifting body at either end of the trailingedge, and rudders mounted in the stabilizers, are indicated at 16 and18. Propulsion means (not shown) may be in the form of a rear propelleror jet motor.

Surfaces 20 and 22, located at either end of the trailing edge, carrysubstantially horizontal outboard pitch control surfaces 24 and 26respectively. These are the surfaces which are normally deflectedupwardly to produce a positive pitching moment and thereby maintain apositive angle of attack. They are located aft of the center of lift. Itwill be noted that the airfoil surface area forward of these controlsurfaces is relatively small. The drooping configuration of surfaces 20and 22 is provided to compensate for excessive rolling moment due tosideslip. It is described in the co-pending application, Ser. No.76,696, filed Sept. 30, 1970, of John P. Kukon and William F. Putman.The axes of rtation of control surfaces 24 and 26 may be somewhat slopedwith respect to the horizontal, but the surfaces are neverthelesssubstantially horizontal in that they perform the function of horizontalcontrol surfaces.

A centrally located substantially horizontal control surface 28 is shownin a downwardly deflected condition.

The center of gravity of the lifting body is located sufficientlyforward that downward deflection of surface 28, acting by itself, wouldproduce a net negative pitching moment.

The same surfaces as shown in FIG. 1 are seen in FIG. 3 whichillustrates how they are adjusted to the condition shown in FIG. 1 by atrim control lever 30.

Lever 30, which is preferably located within reach of the pilot, iscapable of effecting continuous variation of the deflection of surface28 andsimultaneous variation of the deflection of surfaces 24 and 26dependent on the deflection of surface 28.

Lever 30 is arranged to control simultaneously the positions ofthree'pulleys 32, 34 and 36, fastened together and mounted on shaft 38.These are aircraft pulleys having conventional means (not shown) forfastening the control cables at their peripheries in order to avoidslippage. Y

Wrapped around the central pulley 34 is a control cable 40, the uppersection of which is connected to control horn 42 on the upper side ofcontrol surface 28, and the lower section of which is connected to asimilar control horn on the underside of control surface 28. It will beapparent that a rearward movement of lever 30 will produce a downwarddeflection of control surface 28.

Control cable 44 is similarly wrapped around pulley 32, and led by guidesheaves 46, 48, 50 and 52 to another conventional aircraft pulley 54rotatable on a fixed pivot 56 near the rear of the aircraft.

Link 58 is pivotally fastened to pulley 54 at position 60, which isradially spaced from pivot 56 so that rotation of pulley 54 produces amovement of link 58. The other end of link 58 is pivotally fastened toan intermediate point 62 of link 64. A link 66 is slidable lengthwise inconstraint 67 and is pivotally connected to one end of link 64. It isconnected at its other end to bellcrank 68 of control surface 24. Thelower end of link 64 is pivotally connected at 70 to a link 72. Link 72is movable by the pilots stick through control cable 74 and pulley 76 towhich link 72 is connected at a pivot 77 radially remote from the axisof rotation.

Control surface 26 is controlled in the same manner as surface 24. Apulley 78 is interconnected through control cable 80 with pulley 36. Thepilots stick controls pulley 82 through control cable 84. Pulleys 78 and82 respectively control the positions of links 86 and 88 which arerespectively connected to intermediate point 90 and end point 92 of link94. Link 96 is slidable in constraint 97 and is pivotally connected at98 to the upper end of link 94. It interconnects the upper end of link94 with bellcrank 100 on control surface 26.

It will be apparent that the position of the control lever 30 determinespositions of pivots 62 and 90. Since links 58 and 72 both determine thesetting of control surface 24, and since the positions of links 86 and88 determine the setting of control surface 26, assuming a neutralstick, (i.e., assuming the stick to be in the intermediate position itwould be in with all control surfaces in the neutral condition) theadjustment of control lever 30 will move both control surfaces 24 and 26upwardly to effect a preliminary trimming adjustment or settingdepending on the setting of the control lever. Surfaces 24 and 26 areprovided with conventional trim tabs 91 and 93 which adjustautomatically to prevent aerodynamic forces on the control surfaces frombeing transmitted back to the control stick or to lever 30. Thus, whenlever 30 is pulled back, control surfaces 24 and 26 deflect upwardlywithout transmitting a large forward pressure to the pilots stick, andwhen lever 30 is pushed forward, surfaces 24 and 26 deflect downwardlywithout transmitting a large backward pressure .to the stick.

Central surface 28 is preferably provided with a similar trim tab 95 forpreventing large forces on surface 28 from being transmitted back tolever 30. With the pilots stick in a neutral condition, surfaces 24 and26 will be deflected upwardly from neutral when lever 30 is pulledrearwardly, although this may not be the case when the stick is forwardand lever 30 is pulled back.

Rearward adjustment of lever 30 also effects a downwardly deflectedsetting of central control surface 28. About this setting of the controlsurfaces, the pilots stick can be used to vary the positions of surfaces24 and 26 to control elevation and banking of the aircraft in flight.The stick 85 is mounted in a frame 87 pivoted at 89 and 99. Controlcables 74 and 84 are interconnected to form a continuous cable whichpasses around pulleys 101 and 103 which are above the pivot axis offrame 87 and pulleys 105 and 107 which are below the pivot axis. Thus,with a backward pull on the stick, the outboard control surfaces 24 and26 can be simultaneously moved further upwardly to increase the positivepitching moment and thereby increase positively the angle of attack. Theoutboard surfaces can be moved simultaneously downwardly by forwardmovement of the stick. The stick is also pivoted at 109 for I movementfrom side to side. Interconnections are made between the stick and thecable at 111 and 113, and banking can be accomplished by movement of thestick from side to side to produce differential movement of surfaces 24and 26.

All of the stick adjustments are made about variable control surfacesetting determined by thecondition of lever 30. Thus, surface 28 can beused to produce greatly increased lift when deflected downwardly, andthe positions of the outboard control surfaces are automaticallyadjusted upwardly to maintain a suitable deflection angle to compensatefor the downward pitching moment created by the downward deflection ofsurface 28.

FIG. 2 shows a modified lifting body 102 in accordance with theinvention having a central control surface 104 and outboard controlsurfaces 106 and 108, all located between the lateral extremities of thelifting body on the trailing edge. These surfaces are controlled by acontrol system similar to that shown in FIG. 3, and it will be apparentthat similar results are produced when it is noted that control surfaces106 and 108 are located at least partially behind the respectivesweptback portions of the leading edge. Control surfaces 106 and 108 aretherefore preceded by considerably less airfoil surface than precedesthe central control surface 104, and the configuration is such that thebasic lift which is produced as a result of upward deflection of controlsurfaces 104 and 106 contributes to the production of a positivepitching moment.

In the embodiments of both FIGS. 1 and 2, the airfoil surface forward ofthe outboard control surfaces is smaller than that behind the centralcontrol surface, and located toward the stern of the aircraft. Upwarddeflection of the outboard control surfaces produces a downward liftbecause of the basic lift distribution produced by the deflection actingon the airfoil surfaces forward of the outboard control surfaces. Thisdownward liftacts well behind the aircraft center'of lift andcontributes to the generation of a positive pitching moment. Thedownward lift is smaller in magnitude than the basic lift produced as aresult of the action of the central control surface 28 or 104. Thus,there is produced a net increase in lift as a result of a rearward pullon control lever 30.

Pilot actuation of lever 30 before during and after a typical flight istypically as described below with reference to FIGS. 1 and 3.

Prior to take-off, the pilot adjusts lever 30 to such a position thatthe central control surface 28 is deflected downwardly approximatelyone-half its total travel. This deflection increases the aircraft'slifting capacity and hence decreases its take-off speed, thus allowinguse of a shorter runway length. Once in the air and approaching thecruise condition the low speed advantage is no longer necessary, andlever 30 may be returned to a neutral condition. Prior to landing thelever 30 is adjusted by the pilot to provide nearly full downwarddeflection of control surface 28 thereby either reducing his landingspeed by providing additional lift or at a fixed landing speed loweringthe nose of the aircraft thereby affording better visibility and pilotattitude. In all conditions described the pitching moment generated bysurface 28 is small and is at least partially trimmed out by theproportionate upward deflection of surfaces 24 and 26. The use ofdifferent amounts of deflection of surface 28 in landing and take-off isdue to the desire for a higher drag configuration (hence moredeflection) in landing than in take-off.

In addition to the advantages of allowing shortened landing and take-offdistances, use of the centrallylocated control surface 28 for aircraftflight path control increases the pilots ability to control theaircrafts rate of sink. In principle, the centrally-located controlsurface provides direct lift control; that is, the aircrafts aerodynamiclift is controlled and modulated directly without first producing anangular acceleration and consequent angle of attack change to produce alift change. Operation of lever 30 in flight therefore produces a morerapid response in terms of altitude change than would be produced by asystem of control surfaces operating in the conventional manner.

In operation, the pilot actuates thecontrol lever 30 in such a manner asto deflect the trailing edge of the centrally-located control surface 28downwardly when he desires to increase the aircrafts upward rate ofclimb, and correspondingly, deflects it upwardly when he desires-adownward rate of sink. As previously explained, because of the centrallocation of surface 28, the deflections described will produceprincipally lift force changes and little pitching moment changes. Anyresidual pitching moment produced by the centrallylocated surface iscancelled by the outboard control surfaces 24 and 26 through thepreviously-described interconnecting system.

So far, the apparatus has been described as useful for controlling liftwhile avoiding pitching moment changes usually associated with controlof lift. Conversely, the apparatus may be used to adjust the angle ofattack of the aircraft without affecting the net lift. In order toincrease the angle of attack, the pilot adjusts the stick to deflectsurfaces 24 and 26 upwardly, and simultaneously pulls lever 30 back toproduce an upward'lift sufficient to cancel the downward lift whichaccompanies the upward deflection of surfaces 24 and 26. In a similarmanner, the increase in upward lift accompanying a downward deflectionof surfaces 24 and 26 by the stick can be cancelled by pushing lever 30forward.

In summary, this invention provides, in a lifting body, a means forgenerating pitching moment for adjusting and controlling the angle ofattack which does not adversely affect lift. Viewed in another way, theinvention is capable of producing a net increase in lift withoutproducing a substantial change in the pitching moment of the liftingbody.

I claim:

1. A lifting body having a trailing; edge, elevation control means,means providing a first substantially horizontal control surface formingpart of said trailing edge and adapted to be deflected downwardly toimpart a basic lift to the lifting body in flight, a pair of upwardlydeflectable substantially horizontal control surfaces located aft of thecenter of lift, means adjustable to maintain said first control surfacein a downwardly deflected condition and to effect a preliminary trimsetting whereby, at least with the elevation control means in a neutralcondition said upwardly deflectable control surfaces are held in anupwardly deflected condition, said upwardly deflectable control surfacesbeing positioned so that their upward deflection resulting fromadjustment of said maintaining means gives rise to a positive componentof pitching moment, and to a downward lift smaller in magnitude than thebasic lift imparted to the lifting body as a result of downwarddeflection of the first control surface, said adjustable means includingcontrol means for effecting continuous downward variation of thedeflection of said first control surface and simultaneous and dependentupward variation of the deflection of the upwardly deflectable controlsurfaces.

2. A lifting body according to claim 1 in which the elevation controlmeans comprises a pilot-operable control and means interconnecting saidcontrol with the upwardly deflectable control surfaces to effectmovement of said upwardly deflectable control surfaces even when themeans adjustable to effect a preliminary trim setting is held at aparticular adjustment.

3. A lifting body according to claim 1 in which the elevation controlmeans comprises a pilot-operable control and means interconnecting saidcontrol with the upwardly deflectable control surfaces to effectmovement of the upwardly deflectable control surfaces to controlelevation and banking of the lifting body even when the means adjustableto effect a preliminary trim setting is held at a particular adjustment.

4. A lifting body according to claim 1 having a pair of swept-backleading edge portions wherein said upwardly deflectable control surfacesare located on the trailing edge of the lifting body each at leastpartially behind one of said swept-back leading edge portions.

5. A lifting body according to claim 1 in which the center of gravity islocated sufficiently forward that downward deflection of the firstcontrol surface produces a negative pitching moment.

6. A lifting body according to claim 5 in which the elevation controlmeans comprises a pilot-operable control and means interconnecting saidcontrol with the upwardly deflectable control surfaces to effectmovement of said upwardly deflectable control surfaces even when themeans adjustable to effect a preliminary trim setting is held at aparticular adjustment.

- 7. A lifting body according to claim 5 in which the elevation controlmeans comprises a pilot-operable control and means interconnecting saidcontrol with the upwardly deflectable control surfaces to effectmovement of the upwardly deflectable control surfaces to controlelevation and banking of the lifting body even when the means adjustableto effect a preliminary trim setting is held at a particular adjustment.

8. A lifting body according to claim 5 having a pair of swept-backleading edge portions wherein said upwardly deflectable control surfacesare located on the trailing edge of the lifting body each at leastpartially behind one of said swept-back leading edge portions.

1. A lifting body having a trailing edge, elevation control means, meansproviding a first substantially horizontal control surface forming partof said trailing edge and adapted to be deflected downwardly to impart abasic lift to the lifting body in flight, a pair of upwardly deflectablesubstantially horizontal control surfaces located aft of the center oflift, means adjustable to maintain said first control surface in adownwardly deflected condition and to effect a preliminary trim settingwhereby, at least with the elevation control means in a neutralcondition said upwardly deflectable control surfaces are held in anupwardly deflected condition, said upwardly deflectable control surfacesbeing positioned so that their upward deflection resulting fromadjustment of said maintaining means gives rise to a positive componentof pitching moment, and to a downward lift smaller in magnitude than thebasic lift imparted to the lifting body as a result of downwarddeflection of the first control surface, said adjustable means includingcontrol means for effecting continuous downward variation of thedeflection of said first control surface and simultaneous and dependentupward variation of the deflection of the upwardly deflectable controlsurfaces.
 2. A lifting body according to claim 1 in which the elevationcontrol means comprises a pilot-operable control and meansinterconnecting said control with the upwardly deflectable controlsurfaces to effect movement of said upwardly deflectable controlsurfaces even when the means adjustable to effect a preliminary trimsetting is held at a particular adjustment.
 3. A lifting body accordingto claim 1 in which the elevation control means comprises apilot-operable control and means interconnecting said control with theupwardly deflectable control surfaces to effect movement of the upwardlydeflectable control surfaces to control elevation and banking of thelifting body even when the means adjustable to effect a preliminary trimsetting is held at a particular adjustment.
 4. A lifting body accordingto claim 1 having a pair of swept-back leading edge portions whereinsaid upwardly deflectable control surfaces are located on the trailingedge of the lifting body each at least partially behind one of saidswept-back leading edge portions.
 5. A lifting body according to claim 1in which the center of gravity is located sufficiently forward thatdownward deflection of the first control surface produces a negativepitching moment.
 6. A lifting body according to claim 5 in which theelevation control means comprises a pilot-operable control and meansinterconnecting said control with the upwardly deflectable controlsurfaces to effect movement of said upwardly deflectable controlsurfaces even when the means adjustable to effect a preliminary trimsetting is held at a particular adjustment.
 7. A lifting body accorDingto claim 5 in which the elevation control means comprises apilot-operable control and means interconnecting said control with theupwardly deflectable control surfaces to effect movement of the upwardlydeflectable control surfaces to control elevation and banking of thelifting body even when the means adjustable to effect a preliminary trimsetting is held at a particular adjustment.
 8. A lifting body accordingto claim 5 having a pair of swept-back leading edge portions whereinsaid upwardly deflectable control surfaces are located on the trailingedge of the lifting body each at least partially behind one of saidswept-back leading edge portions.